The work proposed represents a systematic, comprehensive approach to the problem of the macromolecular composition of articular cartilage proteoglycans (PGs) and organization of the cartilage matrix. In particular, relationships between PGs of different size will be sought and biochemical, immunological and metabolic differences between them explored. Attention will also be directed toward possible differences in surface receptors of chondrocytes from normal, aged and osteoarthritic cartilage, and to effects of the extracellular milieu (e.g., collagen fibrils) on chondrocyte metabolism. Particular emphasis will be given to changes associated with aging of cartilage and with osteoarthritis.